1. Technical Field
The present invention relates to a groove processing device and a groove processing method.
2. Related Art
A vehicle is provided with a gas cylinder apparatus between a door and a body thereof for reducing a force required by a user to open the door.
The gas cylinder apparatus includes a piston that slides within a cylinder filled with a gas such as air. The piston is fastened to one end portion of a rod, the other end portion of which protrudes from the cylinder to divide the inside of the cylinder into two gas chambers. A check valve is provided inside the piston and a sealing member such as oil seal is attached around an outer circumferential portion of the piston. In addition, to an inner circumference of the cylinder, a cylinder groove protruding from an inner circumferential surface toward an outer circumferential surface side is formed along an axial direction.
In this gas cylinder apparatus, in a compressing process, since a gas in the gas chamber compressed by the piston flows into the other gas chamber through the check valve provided to the piston and the cylinder groove formed to the cylinder, a damping force is rarely generated and the compressing process is promptly performed. On the other hand, in an expanding process, since the check valve is brought into a closed state, the gas in the other gas chamber flows into the gas chamber through the cylinder groove formed to the cylinder. An expansion side damping force is generated by a flow resistance at this time, and thereby the speed in the direction of rod extension is controlled.
Various kinds of devices for forming a cylinder groove to a cylinder of such gas cylinder apparatus have been proposed. For example, a cylinder groove processing device disclosed in Japanese Patent Application Laid-Open Publication No. 09-229123 is configured as follows. The cylinder groove processing device includes: a slide member able to be accommodated in a cylinder, in which a processing roller is rotatably provided in a protruding state and a guide roller is provided coaxially with the processing roller; and a guide member able to be accommodated in the cylinder, in which a main guide surface and first to fourth sub-guide surfaces are continuously provided, wherein the sub-guide surfaces guide the guide roller of the slide member so that the processing roller is brought into a state of non-contact with an inner surface of the cylinder, while the main guide surface guides the guide roller of the slide member so that the processing roller is brought into contact with the inner surface of the cylinder to thereby allow the cylinder to swell outward, and a cylinder groove is formed by the processing roller with relative movement of the slide member with respect to the cylinder and the guide member.
Due to formation of a cylinder groove to an inner circumferential surface of a cylinder, there occurs a possibility that, if a portion inwardly protruding from the inner circumferential surface of the cylinder is formed, after the cylinder is assembled to a gas cylinder apparatus, the portion may cause damage to a sealing member attached around an outer circumferential part of a piston when the piston slides.
An object of the present invention is to provide a device that forms a cylinder groove without forming a portion inwardly protruding from an inner circumferential surface of a cylinder.